Almond shell flour glue extenders

ABSTRACT

Finely divided almond shell flour is used as an extender in plywood- and laminating-adhesives, alone or in combination with other, different, vegetable shell flours.

This application is a continuation of application Ser. No. 830,705, filed Feb. 18, 1986 and now abandoned.

The present invention relates to compositions comprising finely ground almond shells (almond shell flour), alone or in combination with other, different, vegetable shell flours, which compositions are adaptable to use as extenders for aqueous emulsion glues in the formulation of plywood- and laminating-adhesives, and to such adhesives.

The formulation of plywood- and laminating-adhesives from aqueous emulsions of synthetic or natural glues using finely ground natural materials as an extender is well known in the prior art.

Thus, U.S. Pat. No. 3,017,303, incorporated herein by reference, discloses the formulation of such adhesives from emulsions of synthetic phenol-aldehyde or amine-aldehyde resins. The extenders employed in such adhesives include flours produced from nut shells such as walnut (English and black), hickory, palm, and filbert; from pit shells of fruits such as peach, plum, and apricot; and from grain and seed hulls such as oat hulls; and wood flours.

Often, the properties of such extenders may not meet the ever-more rigorous requirements imposed by industry on the adhesives used for preparing plywood, veneers, and other wood laminates. According to the present invention, the provision of finely divided almond shell flour and, particularly, blends thereof with other vegetable shell flours, permits the formulation of extenders which, when used to formulate plywood- and laminating-adhesives with a particular glue formulation, will impart optimum properties to the adhesives, particularly from the point of view of viscosity and stability. Alternatively, the use of the extenders permits one skilled in the art a greater latitude in his choices for blending aqueous glue emulsions when formulating adhesives meeting industry requirements.

The basic requirements for an extender to be used successfully in synthetic resin mixes compounded as adhesive for the assembly of multi-layer plywood and other laminates are as follows:

1. Adequate commercial availability of the extender to fill the large tonnage requirements of the consuming plywood glue mixers at all times.

2. Uniformity of the physical and chemical properties of the extender from shipment to shipment.

3. The development of predictable and uniform rheological properties of glue mixes by the extender used in the mix under varying plant operating conditions, including changes in atmospheric environment.

4. The extender must be free of toxic substances harmful to humans and free of oversized particles, especially those of an abrasive nature. Abrasive extenders dull mill cutting tools and saws.

5. There must be complete compatibility of the extender with all compounding ingredients used in the synthetic resin adhesive composition.

6. Although there have been small quantities of extenders offered for use in the plywood industry that contain substantial percentages of inorganics such as clays, extender formulators prefer raw materials of organic origin.

7. Extenders used in adhesive formulation usually have either an accelerating or decelerating effect on the rate at which glue lines cure under temperature and pressures applied during the pressing of the assembled plies. Extenders that accelerate cure are desired so the rate of production will be increased through the pressing stage.

8. Any organic material used in any extender that is edible by rodents is objectionable. An extender must not attract rats, mice or other rodents.

9. The physical and chemical properties of an extender must remain uniform and unchanged when stored for long periods of time in commercial packages. Some extenders absorb excess moisture at high atmospheric humidity.

10. The mixing of aqueous synthetic resin glue compositions is accomplished commercially with a variety of mechanical mixer types that are generally classified into two varieties, namely, high shear or low shear. High shear mixing machinery is preferred in the plywood industry. The extender being mixed into the gle solution must not cause foaming or dusting. The extender should also mix and disperse readily into the glue solution in short periods of time. Flocculation, coalescence, or separation of the extender in mixed glues causes settling and clogging in the glue transport system, which is unacceptable.

11. The finished glue adhesive is applied to core wood used in plywood assembly by three methods of application, namely roll, spray or curtain coating. Roll coating is now limited to a few plywood mills. Spray coating is most popular, followed by curtain coating, a strong competitor. Extenders are known to cause discontinuous patterns in spray and curtain application systems. Known in the industry as "throw-out" or "blips", such interruptions disturb the continuity of spray and curtain patterns and cause nonuniform glue distribution over the surface of core wood. Such conditions cannot be tolerated in plywood assembly systems.

The finely divided almond shell products of the present invention are derived from a large variety of almond shells that are by-products of almond shelling operations where the almond kernel is separated from the shell. According to the invention, the shells are crushed and reduced in size to flours no coarser than 100 percent through a 150 mesh screen (U.S. Standard Screen) and not finer than 100 percent through a 325 mesh screen (U.S. Standard Screen). When used alone or blended with other low viscosity extender type products used in the formulating of synthetic resin glues for bonding the plies of plywood, these almond shell flours increase the viscosities of the glues to desired flow rates for use in roll, spray, or curtain coating applicators that distribute the glue emulsion evenly and uniformly to ply core wood surfaces.

All almonds harvested in the United States are grown in California. The bulk of each year's crop comes from five counties in the state, namely, Kern, Stanislaus, Merced, Fresno, and Butte, with Kern County growing the largest tonnage. The total crop processed varies from year to year and is reported by the United States Department of Agriculture as total pounds of kernels. For example, a good yearly crop would be 575,000,000 lbs. of kernels and a poor year would yield only 300,000,000 lbs. of kernels. There are about 40 varieties of almonds grown. About 63 percent of the total crop is of the Nonpareil soft shell variety and 9 percent are the hard shell Mission variety, the balance being Merced, Carmel, Peerless, Neplus, and many others. When the nuts are collected after being hulled for processing, they are blended into two general classifications, soft and hard. After cracking, the shell is separated from the kernel. The kernel weight is approximately the same as the shell weight. There is always a small percentage of pieces of hull in the shell that remains in the harvested crop as it comes from the orchards.

The yield of the soft shell in pounds is 5 to 1 compared to the hard variety. Of all the tree nut varieties consumed, almond usage is increasing faster on a per capita basis than any of the other varieties and the yearly ratio of increase is expected to continue for many years. As the demand for almonds goes up, so, also, does the supply of by-product almond shells. The availability of large tonnages of almond shells makes this crop of shells attractive for commercialization, particularly as an ingredient in the manufacture of extenders used by the plywood industry.

One problem which has heretofore severely hindered the industrial use of almond shell flours as extenders or for other purposes is the difficulty encountered in grinding the shells to the requisite particle size. Almond shells have a low bulk density of about 19-20 lbs./ft.³ and, when ground between the discs of an attrition mill such as is conventionally used in the art for grinding vegetable shell product, become overly heated, reach their combustion point, and burst into flame. This problem has been solved by the present applicant by using a mill employing a high speed (about 5000 rpm) rotating disc having hammers on the periphery thereof. The mill, which is commercially available under the mark "BEPEX", has water cooled jackets to maintain operation below the combustion temperature. Coarse materials are automatically returned to the mill until reduced to the desired particle size.

Such impact grinding involves power consumption greater than that required for commercial attrition mills in which materials to be ground are introduced between two discs, rotating in opposite directions at about 1700 rpm and having serrated or textured faces between which the particles are ground. In these attrition mills, size reduction is effected to a considerable degree by interparticle abrasion. The applicant has found that such a conventional mill can also be used to grind almond shells by first blending the shells with vegetable shell materials of greater bulk density and hardness. For example, the blends of almond shell flour with other nut shell flours which are preferred according to the present invention are suitably prepared in this manner.

In any event, in these blends, the size range of the particles of shells such as walnut, filbert, pecan, or the like is the same as that specified earlier for the almond shell flour. Hence, blends meeting these size requirements are conveniently prepared by grinding the shell components together, as discussed above.

Prior to grinding, raw naturally occurring shell materials are first cleaned to remove any residual nut meat and, for example in the case of walnut, to remove the pericarp or fine paper-like web structures found in the shell. The shells are then reduced to a coarse size (about 1/4 inch) convenient for handling by conventional industrial means (conveyors, pneumatic systems) in a pre-grinding or crushing operation. Then, if blends of shell materials are to be prepared, the requisite coarse shell materials are combined in the desired proportion and introduced into an apparatus, e.g. an attrition mill as described earlier for blends of almond shell with harder and denser shells such as walnut or filbert having a bulk density of about 33-35 lbs./ft.³. The higher density shells assist in the attrition of the almond shell without clogging or combustion so that the blends can be directly prepared with economic low power consumption.

Thus, for example, almond shells and English walnut shells are separately coarsely divided into about 1/4 inch size in a hammer mill provided with a screening arrangement for removing nutmeats, pericarp, and other objectionable materials from the ground shells. Forty parts by weight of the coarsely divided almond shells are next blended with 60 parts by weight of coarsely divided walnut shells in a mass which is then conveyed to the "eye" of a conventional attrition mill (e.g. a Bauer attrition mill commercially available from the Combustion Engineering Co., Springfield, Ohio). For grinding shell materials of this kind, the mills are appropriately modified according to U.S. Pat. No. 2,554,450 to introduce cooling water into the mill to maintain the ground shells at a temperature of about 288° F. and to exclude air from the mill by the generation of steam therein. On leaving the mill, the ground mixture of almond and walnut shells is cooled and conveyed to air separators to fractionate the particles. Insufficiently ground material is returned to the mill, typically in an amount about six times the weight of the isolated desired mixed particles.

In the extender blends according to the present invention, the presence of any almond shell flour in the blend will modify the properties of the other component or components of the blend. Hence, the present invention can be considered as pertaining to extenders which comprise anywhere from a few percent to 100 percent of almond shell flour.

However, for the compounding of the plywood- and laminating-adhesives conventionally employed in the art, blends of almond shell flour with other vegetable shell flours will usually contain from 20 to 80 percent by weight of almond shell flour and 80 to 20 percent of other, different vegetable shell flours. Preferred blends will comprise from 30 to 70 percent, or 40 to 60 percent, of almond shell flour, with 70 to 30 percent, or 60 to 40 percent of other, different flours. The most preferred blends according to the invention, in which almond shell flour is combined with English walnut or filbert shell flours, comprise about 40 to 60 percent of almond shell flour.

The formulation of adhesives from aqueous emulsions of synthetic resins and the extenders according to the present invention follows techniques known to those skilled in the art from aforementioned U.S. Pat. No. 3,017,303. As there described, suitable phenol-aldehyde glues (e.g. phenol-aldehyde, resorcinol-aldehyde) having a solids content of 40-50 percent by weight (typically 42 percent) are prepared by reacting one molar part of phenol with two molar parts of an aldehyde such as formaldehyde in the presence of an alkali such as sodium hydroxide at 85° C.-100° C. until the proper viscosity is reached and then diluting with water as desired. The patent similarly exemplifies the production of a typical amine-formaldehyde glue (e.g. urea-formaldehyde, melamine formaldehyde) by reacting 160 parts by weight of formalin (37%), 2 parts by weight of ammonium hydroxide (28%), and 1 part by weight of sodium acetate at 90° C. for 2 hours. The pH is adjusted by addition of more ammonium hydroxide if necessary and excess water is removed by vacuum distillation to reach the proper solids content.

The combination of such synthetic resin emulsions with the extenders of the present invention also takes place as disclosed in U.S. Pat. No. 3,017,303. The plywood- and laminating-adhesives to be prepared are typically characterized by the ratio by weight of resin to extender to water therein. For typical 40-50% phenolic resin emulsions, a high quality resin/extender/water ratio is taught to be 5/1/1.75. However, as for the adhesives of the prior art, the quantities of extender and water can be increased according to the present invention to define compositions having ratios of 5/1.2-2.8/1.8-5.5, for example. As known to those skilled in the art and as discussed in the aforementioned patent, satisfactory adhesives can be formulated with ratios within or without the aforementioned ratios, depending on the resin system, its concentration in the emulsion, the nature of the extender and its state of subdivision, other components such as fillers, on pH, and on the conditions of mixing (e.g. high shear as in a Cowles mixer or low shear as in a paddle mixer), as well as other operational factors such as assembly time, pre-press operations, press temperature, and pressure and curing time.

It is noted that contemporary adhesive compositions are formulated by the addition of caustic soda and/or other alkalis thereto, often to reach a pH of as high as 12. This obviates any need to adjust, control, or alter the pH of the naturally occurring components of the extender to overcome natural pH variations therein, as was often heretofore required in the prior art. Also, contemporary adhesive formulations commonly include a tackifying agent (often characterized as a "filler") which is conveniently included to provide green strength to plywood and other laminates during handling prior to curing of the adhesive compositions under heat and pressure.

A better understanding of the present invention and of its many advantages will be had from the following specific examples of extenders and adhesive compositions made according to the present invention and from their comparison with prior art materials.

The superior properties of the extender compositions of the invention are evident from tests evaluating their water absorption and the viscosity enhancement and stability which they impart to adhesives formulated therewith. The tests are routinely performed in the art to evaluate the acceptability of an extender for use in synthetic glue solutions that in turn are applied to the surfaces of plywood core veneer prior to assembly of the plies of plywood before being cured under heat and pressure.

WATER ABSORPTION TEST METHOD

1. Weigh out 15.0 grams of the sample to be tested. Put the test sample into a beaker large enough to allow for the water addition and hand mixing - at least 100 ml.

2. Accurately measure 50.0 ml. of tap water in a graduated cylinder.

3 Slowly add water to the test sample from the graduated cylinder with frequent hand mixing using a metal or glass stirrer. Initial water and additions should be approximately 5 ml., followed by stirring until the mixture becomes visibly damp, at which point water additions should be in 0.5 to 1.0 ml. increments.

4 After each water addition and stirring, the beaker should be rotated slightly more than 90°. The end point of the test is established when some or all of the water addition freely flows from the test sample down the inside of the beaker. Any such free flowing water should be returned to the graduated cylinder. Determine the amount of water left in the graduated cylinder in ml. at the conclusion of the test and subtract this amount from 50.0. Report this difference as the water absorption expressed in ml.

The results of tests on the water absorption of a variety of typical organic flours used as extenders in plywood-and laminating-adhesives is reported below in Table 1.

                  TABLE 1                                                          ______________________________________                                                          MESH    H.sub.2 O   MOIS-                                     EXTENDER         SIZE    ABSORPTION  TURE                                      ______________________________________                                         1.  Hard Almond      200     39.2      2.8%                                    2.  Soft Almond      200     46.6      2.6                                     3.  English Walnut   200     29.8      1.2                                     4.  Filbert Shell Flour                                                                             200     26.7      3.0                                     5.  Pecan Shell Flour                                                                               200     31.6      6.0                                     6.  "CO-COB" (Quaker Oats)   27.6      7.8                                     7.  25% Soft Almond and                                                                             200     33.0      3.0                                         75% English Walnut                                                         8.  25% Hard Almond and                                                                             200     34.4      3.4                                         75% English Walnut                                                         9.  Cherry Pit Flour 200     24.8      5.0                                     10. Coconut Shell Flour                                                                             200     38.4      7.0                                     11. "GLUFIL, HL"     300     36.0      4.0                                         (Commercial extender)                                                      12. 50% English Walnut and                                                                          200     44.0      3.8                                         50% Soft Almond Shell                                                      13. 50% English Walnut and                                                                          200     39.4      3.3                                         50% Hard Almond Shell                                                      14. 50% English Walnut/                                                                             200     41.0      2.6                                         25% Soft Almond Shell/                                                         25% Hard Almond Shell                                                      15. Alder Bark Flour 200     36        5.0                                     ______________________________________                                    

Water absorption tests for plywood extenders yield a relative value. The test is not an accurate quantitative determination. However, the test is simple and consumes very little time and shows some correlation with viscosity building values of the different plywood glue extenders (cf. following Table 2).

"GLUFIL, HL", the commercial extender listed in the Table, is the quality standard extender of the industry. It comprises 95% of -325 mesh English walnut shell flour densified and reduced in size by methods taught in U.S. Pat. No. 3,429,770. This standard material has a water absorption of 36. Soft almond shell flour has a water absorption of 46.6, while hard almond shell flour has a water absorption of 39.2. When these flours are blended with walnut shell flours, which have an absorption capacity of 29.8, the blends have absorption capacity greater than the "GLUFIL, HL" standard, namely 44, 39.4 and 41.0, respectively. This demonstrates that the almond shell products are absorption builders for lower absorption walnut shell flour and other low water absorption flours used in the plywood industry.

The "CO-COB" material identified in the Table and the "FURAFIL" of following Table 2 are also commercial extenders prepared from the residues of natural products such as corn cobs, oat hulls, etc. after extraction to remove furfural therefrom.

For testing viscosity enhancement and stability, typical adhesives are formulated according to the following recipe, using a high speed mixer.

    ______________________________________                                         Add To Mixer Water             150 gms.                                        Turn Mixer On                                                                  Add          Wheat Flour ("filler")                                                                            50 gms.                                                     Extender           75 gms.                                        Mix 3 Minutes                                                                  Add          Resin (phenol-formaldehyde)                                                                      225 gms.                                        Mix 2 Minutes                                                                  Add          50% Caustic        33 gms.                                        Mix 15 Minutes                                                                 Add          Resin (phenol-formaldehyde)                                                                      450 gms.                                        Mix 5 Minutes                                                                  Total Mix                      983 gms.                                        ______________________________________                                    

A 400 ml. beaker Is filled with the resulting mix for viscosity testing. The balance of the mix is discarded. Testing is done on a Brookfield Viscometer immediately after mixing is finished and time/temperature/viscosity are recorded. Then the mix is stirred and temperature and viscosity are redetermined after one hour and after 24 hours of storage at room temperature (approximately 72° F.). Viscosities can be measured using #4 or #5 spindles at 10 or 20 rpm. A #5 spindle at 10 rpm. is generally used.

Mix viscosities are relative, and vary dramatically with different components such as the wheat flour filler, the extenders, and water sources. "Standard" batches are run at the beginning and end of all test series.

Following Table 2 shows the viscosity values developed in such testing by various extenders.

                  TABLE 2                                                          ______________________________________                                                              #5 Spindle                                                                     VISCOSITIES @                                                                  10 RPM (cps)                                              EXTENDER               (Initial)                                                                               (24 hrs.)                                      ______________________________________                                         1.  "GLUFIL, HL" (Industry Standard)                                                                      5,000    7,500                                      2.  Soft Almond flour (200 Mesh)                                                                          11,400   13,700                                     3.  Hard Almond flour (200 Mesh)                                                                          8,800    9,500                                      4.  50% Soft Almond/50% Walnut                                                                            4,500    6,500                                          Shell flour (200 Mesh)                                                     5.  50% Hard Almond/50% Walnut                                                                            5,100    6,200                                          Shell flour (200 Mesh)                                                     6.  25% Soft Almond/25% Hard Almond/                                                                      3,800    5,000                                          50% Walnut Shell flour (200 Mesh)                                          7.  "FURAFIL" (Commercial Extender)                                                                       3,650    4,700                                      ______________________________________                                    

The viscosities shown for the "GLUFIL, HL" extender (No. 1) in the above Table are within a range for normal commercial application and can be adjusted for use in any one of the three commercial glue spreading methods used in the plywood industry, namely roll, spray, or curtain coaters. The percentage change in the standard viscosity at the end of a 24 hour standing period is greater for the "GLUFIL, HL" industry standard than for any of the other listed extenders that contain almond shell flours as part of their composition. This means that the use of plywood extenders containing almond shell impart greater stability to glues than "GLUFIL, HL", the industry standard.

Glue mixes compounded according to the glue formulation used for these testing purposes with the soft and hard almond shell flours only (Nos. 2, 3) have viscosities too high for practical commercial use. However these flours can be used alone as extenders for plywood-and laminating-adhesives by suitable alteration of the glue formula now routinely used in the plywood industry. As has been previously shown (water absorption Table 7), the soft almond flour has a higher water absorption than the hard almond, 46.6 and 39.8, respectively.

The glue viscosities of these two products, when blended with walnut shell flour or other flours, often show reverse orders of magnitude in viscosity as illustrated by extenders Nos. 4, 5, and 6 in the above Table 2. Extenders Nos. 2 and 3 demonstrate the tremendous viscosity building capacity these products have when used in standard synthetic phenol-formaldehyde plywood glues.

The performance of blended shell compositions as shown in the Table 2 will be very similar when used in urea-formaldehyde glues.

Following Table 3 compares the plywood properties of seven commercial plywood glue extenders now being sold to the plywood industry with samples of compositions comprising soft and hard almond shell flour (-200 mesh in size).

There are some striking differences in the properties of these different materials. There are three walnut shell flour products in the group, a 200 mesh size, a 325 mesh size, and "GLUFIL, HL" (a 300 mesh size commercial product). All three products are very similar in physical properties except for screen mesh size that can be observed from the screen analysis. Products Nos. 1 and 2 are light tan in color. Products Nos. 3, 4, 5, and 7 are dark brown in color and when added to glue mix and the mix spread on plywood veneer, the glue line is darker in color and remains darker in color in the finished plywood product. A dark glue line is preferred by the plywood industry because wood failure testing for product quality is determined much more accurately on dark colored glue in sheared test pieces. Indeed, it is common in the art to add a small amount of carbon black to the extender during blending in order to deepen its color.

The ash content of extenders is an important value. These values vary widely; for example, product No. 4, a composite of three components, has a very low ash content of 1/2-1 percent. In contrast, other composites Nos. 5 and 6 both have very high ash contents of 12-15 percent and 35-40 percent, respectively. The ash of product No. 5 is silica, which is very abrasive to cutting tools and saws used in plywood manufacture. The ash in No. 6 is clay which has a high silica content and is also abrasive. Product No. 4, having a very low ash content, is a non-abrasive extender. The screen mesh size (grain or particle size values) of extenders is of interest to plywood glue formulators. The presence of large particles or grains, i.e. anything larger than that which will pass through a 150 mesh screen, causes glue spreading problems. These particles clog spray nozzles and develop discontinuances in curtain coater patterns. Extender No. 6, a very coarse product, does not meet industry extender standards, yet it is sold and used in some plywood mills on price. The particle size range of No. 7 is borderline and is used where quality can be sacrificed. The commercial product No. 4 containing almond shell flour is made to top size fineness of not more than 10 percent of the product weight being retained on a 200 mesh screen, which is acceptable to plywood glue formulators.

                                      TABLE 3                                      __________________________________________________________________________     PHYSICAL PROPERTIES OF EXTENDERS                                                             %             Bulk Density On   SCREEN ANALYSIS                  PRODUCT       MOISTURE                                                                              pH                                                                               % ASH                                                                               Lbs./cu. ft.                                                                          COLOR 100 mesh                                                                            -100/+200                                                                               Thru 200                __________________________________________________________________________                                                            mesh                    1 Walnut Shell Flour                                                                         5-8    5 0.5  40     Lt. Tan                                                                              0    10% max. 90% min.                  200 Mesh                                                                     2 Walnut Shell Flour                                                                         5-8    5 0.5  35     Lt. Tan                                                                              0    Tr.      100%                      325 Mesh                                                                     3 "GLUFIL, HL"                                                                               5-8    5 0.5  40     Dk. Brown                                                                            0    Tr.      100%                      300 Mesh                                                                       Commercial Extender                                                          4 25% Soft Almond/                                                                           4-8    5 0.5-1.0                                                                             35     Dk. Brown                                                                            0    10% max. 90% min.                  25% HardAlmond/                                                                50% Walnut Shell Flour                                                         200 Mesh                                                                     5 "FURAFIL"   Varies -                                                                              2.5                                                                              13-15                                                                               30     Very Dk.                                                                             Tr.  10% max. 90% min.                  (Commercial)                                                                               currently            Brown                                         (Cocob & Phenofil)                                                                         20+                                                                200 Mesh                                                                     6 "PLY-X" (Commercial)                                                                       5-9    6 35-40                                                                               35     Off White                                                                            10%  25%      65% min.                  100 Mesh                               max.                                  7 Pecan Shell Flour                                                                          5-8    5 3-4  35     Dk. Brown                                                                            5-10%                                                                               20-25%   70% min.                  (Hammon's)                                                                     100 Mesh                                                                     8 Hard Almond Shell                                                                          3-8    5 1.0  30     Lt. Tan                                                                              0    10% max. 90% min.                  Flour -200 Mesh                                                              9 Soft Almond Shell                                                                          3-8    5 1.0  30     Lt. Tan                                                                              0    10% max. 90% min.                  Flour -200 Mesh                                                              __________________________________________________________________________

The almond shell flours of the present invention are of particular utility for blending with filbert shell flours in the manufacture of extenders according to the present invention.

Ideal weather conditions for the growing of filbert nuts are found in the West central region of Oregon, the only part of the United States where filbert nuts are grown. By comparison with other tree nut crops, the yearly crop of filberts is plus or minus 18,000 tons/yr. (2,000 lbs./ton). The crop is reported by the weight of shell nuts harvested. There is a small number of processors who merchandise each year's crop as "nuts in the shell" and as kernels removed from the shell. The normal yearly accumulation of by-product filbert shells is 6,000 to 7,000 tons. Some are sold as fuel and the balance is consumed in cattle feed.

The Northwestern plywood industry is located in the Province of British Columbia, Canada, and in Washington, Oregon, and northern California. By-product filbert shell flour, when properly blended with a viscosity building flour such as almond shell flour, makes an economically attractive and useable extender for plywood adhesives since the by-product filbert shells are centrally located in the northwestern plywood industry area.

Attempts have been made to grind these shells to flour and sell the flour as an extender for use in synthetic resin adhesive glues for structuring plywood. The plywood industry could not use filbert shell flour because of very low water absorption and poor viscosity build-up in adhesive glue mixes.

Following Tables 5, 6, and 7 report viscosity data for filbert shell flour blended with almond shell flour. The almond flour provides the necessary viscosity enhancement to bring the blends into workable viscosity ranges for application of glue adhesives to core wood used in the assembling and gluing of plywood.

For obtaining the reported data, glue mixing was carried out as earlier described with samples of 1000 grams of the glue mix. Constant room temperatures of 70° F. ±2° F. were maintained. For measuring viscosity, spindle #4 at 12 rpm was used in the Brookfield Viscometer. Calculated values are expressed in centipoises. A commercial "PF-547" phenolic resin having approximately 43 percent solids content was diluted with water and mixed with the various extender samples, and with the other ingredients.

                  TABLE 5                                                          ______________________________________                                         GLUE VISCOSITY                                                                              Resin  Viscosity (cps)                                                         quantity                                                                              After 1 Hr.                                                                              After 24 hrs.                                                 used in                                                                               Activation with                                                         initial                                                                               spindle #4                                                 Extender       glue mix 12 rpm    12 rpm                                       ______________________________________                                         1   "GLUFIL, HL"       high   5,500   6,700                                        Commercial         medium 7,500   13,000                                       Extender                                                                   2   200 Mesh Filbert   high   1,500   1,250                                        Shell Flour        medium 4,750   8,000                                    3   325 Mesh Filbert   high   2,650   3,000                                        Shell Flour        medium 5,100   7,500                                     4   200 Mesh Filbert                                                                                 high   8,700   6,500                                        percent                                                                         325 Mesh Almond                                                                                  medium 10,000  8,000                                        percent                                                                     5   200 Mesh Filbert                                                                                 high   4,500   5,000                                        50 percent                                                                      325 Mesh Almond                                                                                  medium 9,000   12,250                                       50 percent                                                                  6   200 Mesh Filbert                                                                                 high   2,000   3,250                                        80 percent                                                                      325 Mesh Almond                                                                                  medium 7,500   10,250                                       20 percent                                                                  7   325 Mesh Filbert                                                                                 high   8,250   10,500                                       20 percent                                                                      325 Mesh Almond                                                                                  medium 13,750  15,000                                       80 percent                                                                  8   325 Mesh Filbert                                                                                 high   6,000   6,500                                        50 percent                                                                      325 Mesh Almond                                                                                  medium 8,500   11,500                                       50 percent                                                                  9   325 Mesh Filbert                                                                                 high   2,500   2,000                                        80 percent                                                                      325 Mesh Almond                                                                                  medium 7,000   8,500                                        20 percent                                                                 ______________________________________                                    

                  TABLE 6                                                          ______________________________________                                         GLUE VISCOSITY                                                                 Extender          1 hr. after mixing:                                          ______________________________________                                         1   "GLUFIL, HL"          Viscosities are in the median                            Commercial Extender   range for commercial use.                            2   200 Mesh Filbert      Viscosities are below accept-                            Shell Flour           able commercial use ranges.                          3   325 Mesh Filbert      Viscosities of this finer size                           Shell Flour           product are low for normal                                                     commercial use. Will work in                                                   specialty applications only,                                                   with high viscosity resin.                            4   200 Mesh Filbert 20% Viscosities of this blend con-                                                 taining almond flour are ac-                             325 Mesh Almond 80%   ceptable in limited number of                                                  applications.                                         5   200 Mesh Filbert 50%  Viscosities are in a normal                             325 Mesh Almond 50%   working range.                                        6   200 Mesh Filbert 80% Viscosities are in low range                                                   useable only with high                                   325 Mesh Almond 20%   viscosity resin glue.                                 7   325 Mesh Filbert 20% The 325 mesh size blend of                                                     80%/20% almond and Filbert                               325 Mesh Almond 80%   flours produce excessive vis-                                                  cosities. Could be used with                                                   very low viscosity resins.                            8   325 Mesh Filbert 50% Median viscosities develop                                                     with the use of this blend                               325 Mesh Almond 50%   in normal glue mixes.                                 9   325 Mesh Filbert 80% Viscosities of this finer size                                                 product are low for normal                               325 Mesh Almond 20%   commercial use. Will work                                                      in specialty application with                                                  high viscosity resins.                               ______________________________________                                    

                  TABLE 7                                                          ______________________________________                                         GLUE VISCOSITY                                                                 Extender          After standing 24 hours:                                     ______________________________________                                         1   "GLUFIL, HL"          Median viscosities are normal                            Commercial Extender   in standard resin glue form-                                                   ulations.                                            2   200 Mesh Filbert      Shows instability on aging.                              Shell Flour           Viscosity much too low.                              3   325 Mesh Filbert      Viscosities are below commer-                            Shell Flour           cial use levels.                                      4   200 Mesh Filbert 20% Viscosities are above normal                                                   use ranges. Lack of stabil-                              325 Mesh Almond 80%   ity is restrictive. Formulate                                                  with low viscosity resin.                             5   200 Mesh Filbert 50%  Median viscosities are normal                           325 Mesh Almond 50%   for commercial use.                                   6   200 Mesh Filbert 80%  Same as #5. Viscosity varia-                            325 Mesh Almond 20%   tions excessive.                                      7   325 Mesh Filbert 20% Special formulation could                                                      adapt this high viscosity                                325 Mesh Almond 80%   blend.                                                8   325 Mesh Filbert 50%                                                                                Same as 190 1.                                           325 Mesh Almond 50%                                                         9   325 Mesh Filbert 80% This blend shows lack of stab-                                                 ility due to high percentage                             325 Mesh Almond 20%   of fine Filbert Shell Flour.                                                   Can be used with high viscos-                                                  ity resins.                                          ______________________________________                                    

The American plywood industry manufactures plywood to quality standards dictated by the American Plywood Association (APA) located in Tacoma, Wash. The standard adhesive policy of this Association was established and published on Mar. 1, 1980. Section "F" of this publication entitled "Plant Trials of Approved Adhesive for Extenders" sets approval standards for plywood glue performance and at the same time these procedures are effective in screening the quality and performance of extenders used in such plywood glues.

An extensive testing program using the APA standard test procedures was planned and completed to show extender values and performance of a number of compositions containing various amount of almond shell flour blended with walnut shell flour or filbert shell flour. The glue formulations and mixing procedures used for these tests are generally the same for the various resins used by the industry. The procedure for making the glues using Georgia Pacific phenol-formaldehyde plywood glue "GP-553" resin (42 percent non-volatile solids) is shown below. Different formulations are shown for high shear mixing (e.g. using a Cowles mixer) and for low shear mixing (e.g. using a paddle stirrer).

    ______________________________________                                                          High-shear                                                                              Low-shear                                            Mix Ingredients and Mix Times                                                                     (Parts by Weight)                                           ______________________________________                                         Water              725        625                                              "Glu-X" wheat flour filler                                                                        200        200                                              mix until wet                                                                  Extender           350        350                                              mix until wet (3 minutes)                                                      "GP 553" Resin (42 percent N.V.                                                                   .sup. 900.sup.a                                                                           .sup. 900.sup.a                                  solids) mix 3 minutes                                                          Sodium hydroxide (50 percent)                                                                     135        135                                              mix 15 minutes                                                                 "GP 553" Resin (42 percent N.V.                                                                   1800       1800                                             solids) mix 2 minutes                                                          Total mix          4110       4010                                             ______________________________________                                         Mix Characteristics                                                                               Percent                                                     ______________________________________                                         Resin solids       27.6       28.3                                             Filler.sup.b       7.7        7.8                                              Extender.sup.b     4.4        4.5                                              Sodium hydroxide   1.6        1.7                                              Total mix solids   41.3       42.3                                             Total mix water    58.7       57.7                                             Total mix          100.0      100.0                                            ______________________________________                                          .sup.a The premix resin is varied to meet mix viscosity requirements.          .sup.b The filler and extender are assumed to have 10 percent moisture         content in these calculations.                                           

Following Table 8 evaluates various glue extenders from the point of view of wood failure averages.

                  TABLE 8                                                          ______________________________________                                         GLUE EXTENDERS BY WOOD FAILURE AVERAGES                                                             %                                                         Extender             Average Wood Failure                                      ______________________________________                                         1   "GLUFIL, HL"             95%                                                   Conventional Extender                                                       2   20% 325 Mesh Filbert Flour                                                                             94%                                                   80% 325 Mesh Almond Flour                                                   3   80% 325 Mesh Filbert Flour                                                                             92%                                                   20% 325 Mesh Almond Flour                                                   4   50% 325 Mesh Filbert Flour                                                                             91%                                                   50% 325 Mesh Almond Flour                                                   5   80% 200 Mesh Filbert Flour                                                                             88%                                                   20% 325 Mesh Almond Flour                                                   6   50% 200 Mesh Filbert Flour                                                                             93%                                                   50% 325 Mesh Almond Flour                                                   7   20% 200 Mesh Filbert Flour                                                                             92%                                                   80% 325 Mesh Almond Flour                                                  ______________________________________                                    

The American Plywood Association's passing requirement for wood failure is 85 percent. In the above test series, all seven test blends passed with a satisfactory margin of safety. Wood failures above 90% are normally classified as of excellent quality. Only one blend (No. 5) had a wood failure of less than 90%-at 88%. This product, having a below 90% wood failure, was adversely depressed by the 80% filbert shell flour in it which, by itself, develops poor wood failure. The constructive effect of almond shell flour in the above blends is evident.

Plywood mills usually pre-press plywood panels in load-bundle fashion prior to hot pressing. Cold glue tack on the glue line sticks to the panels so the separate veneers stay together during loading of hot press pre-loaders and the hot presses which have relatively narrow openings, 30 to 50 in number. Poor pre-press tack prevents proper loading procedures and results in reject plywood panels. The degree of pre-press tack in part is determined by resin properties and solvent loss after adhesive application to the veneer. The time after adhesive application includes stand time without pressure and pre-press time under pressure. The adhesive mix solvent loss is influenced by extender properties, water in the glue mix, veneer moisture, and temperature and mix viscosities. The numerical value of pre-press properties is determined by an unsophisticated test. The stand/pre-press/stand times used in the test typify the worst possible conditions for prepress. Fifty pounds pull in the test causes complete wood failure and therefore there is no need to exceed this value. If, under any of the conditions of the test, approximately 40-55 lbs. pull an be realized, then prepress is considered to be satisfactory.

Four typical extenders were tested for the prepress characteristics reported in following Table 9. All the extenders tested have satisfactory values.

                                      TABLE 9                                      __________________________________________________________________________     Extender Characteristic Data with "GP-553" Resin                                                   #1     #2       #3       #4                                                    Commercial                                                                            70% Walnut                                                                              50% Walnut                                                                              30% Walnut                                            Extenter                                                                              30% Almond                                                                              50% Almond                                                                              70% Almond                        Characteristic                                                                            Basis    "FURAFIL"                                                                             (200 Mesh)                                                                              (200 Mesh)                                                                              (200 Mesh)                        __________________________________________________________________________     Raw Material                                                                              Source   Blend  Nut Shell Blends                                                                        Nut Shell Blends                                                                        Nut Shell Blends                  Ash        %         13      1        1        1                               High-shear std. mix -                                                                     % of total                                                                               34     37       48       48                               premix resin                                                                              mix resisn                                                          High-shear mix,                                                                           Viscosity                                                           mix stability                                                                             at 25° C.                                                    Initial    cps      3650   3050     2300     2950                              After 24 hrs.                                                                             cps      4700   4100     3850     3200                              After 48 hrs.                                                                             cps      5250   3800     3500     --                                After 1 Week                                                                              cps      5400   5000     --       4100                              Curtain - std. mix                                                                        S--satisfactory                                                                         S      S        S        S                                            U--unsatisfactory                                                   Spray - std. mix    S      S        S        S                                 Low-shear paddle mix                                                                      Initial cps                                                                             6000   3700     3850     7200                              viscosity                                                                      Premix resin                                                                              % of total                                                                               30     40       40       45                               (low-shear mix)                                                                           mix resin                                                           Roll coater                                                                               S--satisfactory                                                                         S      S        S        S                                 Prepress                                                                       (stand/prepress/stand)                                                                    Lbs.-pull                                                           3/3/0 minutes                                                                             50 max.   50     26        7       12                               5/5/0 minutes                                                                             50 max.   50     50       50       50                               7/3/4 minutes                                                                             50 max.   50     50       50       50                               __________________________________________________________________________

At least 20 plywood panels were made with each of the four extenders shown in Table 9. Ten tension-shear specimens per panel were prepared for each panel with five designed to pull with lathe checks open and 5 with lathe checks closed. All extenders made excellent plywood, as reported below in Table 10.

                                      TABLE 10                                     __________________________________________________________________________     Plywood Shear Test Performance                                                 Averages in Percent Wood Failure                                                             #1     #2     #3     #4                                                        Commercial                                                                            70% Walnut                                                                            50% Walnut                                                                            30% Walnut                                                Extender                                                                              30% Almond                                                                            50% Almond                                                                            70% Almond                                                "FURAFIL"                                                                             (200 Mesh)                                                                            (200 Mesh)                                                                            (200 Mesh)                                                psi                                                                               % WF                                                                               psi                                                                               % WF                                                                               psi                                                                               % WF                                                                               PSI                                                                               % WF                                     __________________________________________________________________________     Plywood cure rate test                                                         (Hot press time)                                                               21/2 minutes  121                                                                               .sup.a 76.sup.T                                                                    186                                                                               91  171                                                                               94  196                                                                               90                                       23/4 minutes  151                                                                                81.sup.T                                                                          161                                                                               98  182                                                                               98  184                                                                               98                                       3 minutes     147                                                                                .sup.b 67.sup.D                                                                   232                                                                               91  188                                                                               94  200                                                                               96                                       31/2 minutes  135                                                                               84  208                                                                               94  188                                                                               96  213                                                                               98                                       4 minutes     170                                                                               97  205                                                                               94  195                                                                               95  180                                                                               94                                       Assembly time test at 80° F.                                            10 minutes     95                                                                               95  223                                                                               85  181                                                                               94  167                                                                               95                                       20 minutes    170                                                                               95  205                                                                               94  195                                                                               95  180                                                                               94                                       40 minutes     84                                                                               97  158                                                                               96  183                                                                               92  165                                                                               90                                       Assembly time at 120° F.                                                10 minutes     97                                                                                82.sup.T                                                                          158                                                                               98  146                                                                               98  194                                                                               92                                       20 minutes    133                                                                               89  178                                                                               90  135                                                                               99  184                                                                               99                                       40 minutes    127                                                                               95  156                                                                               .sup.  72.sup.D*                                                                   187                                                                               93  190                                                                               86                                       __________________________________________________________________________      .sup.aT Transfer; undercure appearance                                         .sup.bD Poor or no transfer; dried out appearance                              *Poor wood                                                               

In Table 10, extender No. 2 showed some minor under-cure as measured by percent wood failure at short assembly times (10 minutes) at 80° F. Extender No. 2 showed some significant dryout at the longest assembly time (40 minutes) at 80° F., which was due to poor wood quality. All of the data relating to assembly time at 80° F. for the extenders of the invention were comparable to the results obtained with "FURAFIL".

At 120° F., the control "FURAFIL" showed some minor under-cure at the shorter assembly time (10 minutes) as measured by the distribution of percent wood failures. Wood failures were excellent for test samples Nos. 2, 3, and 4.

Test extenders Nos. 2, 3, and 4 were better than the No. 1 "FURAFIL" commercial extender in cure rate. Ash content--Sample No. 1, the control, has a very high ash content. The ash content of samples Nos. 2, 3, and 4 are maximum one percent (1%).

The quantity of pre-mix resin used in formulations Nos. 3 and 4 is excessive, causing low viscosity values. Mix stability, roll coating, curtain coating, and spray coating all performed satisfactorily with all samples. Low shear paddle mixes wer all normal for all samples. Pre-mix resin in low-shear mixing was normal for all samples.

Prepress results--(Values given at stand/prepress/stand)

At 3/3/0 - samples 2, 3, and 4 were weak.

At 5/5/0 - normal plant practice was represented.

At 7/3/4 - Pull values were maximum and excellent at 50 lbs.

A series of viscosity and shear performance tests were completed on four different types of almond shell flours. Two samples were made from hard almond shells in two mesh sizes, 200 mesh and 325 mesh. The other two samples were prepared from soft almond shells in the same mesh sizes, 200 mesh and 325 mesh. This series of tests was made to demonstrate that standard quality commercial plywood glued with adhesives containing only almond shell flour as the extender in glue formulation is feasible.

Following Table 11 shows the glue formulations while Table 12 reports the shear test values.

                                      TABLE 11                                     __________________________________________________________________________     ADHESIVE GLUE FORMULATION AND MIXING PROCEDURE                                 (Quantities shown are in pounds)                                                         #1       #2       #3       #4                                                  -200 Mesh Hard                                                                          -325 Mesh Hard                                                                          -200 Mesh Soft                                                                          -325 Mesh Soft                            Ingredient                                                                               Almond Shell                                                                            Almond Shell                                                                            Almond Shell                                                                            Almond Shell                              __________________________________________________________________________     Water     251.5    251.5    251.5    251.5                                     Extender  74       74       74       74                                        Wheat Flour                                                                              59       59       59       59                                        Resin - PF-547                                                                           314      314      314      314                                       MIX 5 MINUTES                                                                  50% NaOH  37       37       37       37                                        MIX 5 MINUTES                                                                  Soda Ash  5.5      5.5      5.5      5.5                                       MIX 10 MINUTES                                                                 Resin PF-547                                                                             259      259      259      259                                       MIX 5 MINUTES                                                                  TOTAL WEIGHT                                                                             1,000    1,000    1,000    1,000                                     TO MIX                                                                         One Hour Mix                                                                             4,400    4,000    6,500    4,500                                     Viscosity-cps                                                                  27° C. Spindle                                                          #4 @ 12 rpm                                                                    24 Hr. Mix                                                                               6,000    9,000    8,750    4,500                                     Viscosity-cps                                                                  27° C. Spindle                                                          #4 @ 12 rpm                                                                    __________________________________________________________________________

                  TABLE 12                                                         ______________________________________                                         PLYWOOD SHEAR TEST PERFORMANCE                                                 Averages of Percent Wood Failure                                               Veneer at 6 Percent MG                                                         Extender          Glue Spread 60 lb./MDGL                                      ______________________________________                                         -200 Mesh Hard Almond Shell                                                                      89%                                                          -325 Mesh Hard Almond Shell                                                                      93%                                                          -200 Mesh Soft Almond Shell                                                                      92%                                                          -325 Mesh Soft Almond Shell                                                                      91%                                                                            91.5% Average                                                ______________________________________                                    

Observations on the performance of all four almond shell flours listed in Table 11 are as follows:

1. Glue mixing was performed with more than a normal amount of premix resin in making of the glue.

2. Glue viscosities developed were within normal commercial working ranges.

3. Wood failures listed in Table 12 averaged b 91.5%. An 85% wood failure average passes the American Plywood Association specification requirements. 

What is claimed is:
 1. A composition of matter adaptable to addition to a plywood- and laminating-adhesive as an extender therefor particularly to improve the viscosity and stability properties thereof, said composition comprising from 30 to 70 percent by weight of almond shell flour at its naturally occurring pH and having a particle size no coarser than 100 percent through a 150 mesh screen and no finer than 100 percent through a 325 mesh screen and from 70 to 30 percent by weight of a different nut shell flour selected from the group consisting of walnut shell flour, pecan shell flour, and filbert shell flour.
 2. A plywood and laminating-adhesive composition comprising an aqueous emulsion of a phenol-aldehyde resin glue or an amine-aldehyde resin glue and, as an extender therefor, a composition as in claim
 1. 